Object
An object is an instance of a class stored in a set of memory locations.
Related concepts: ClassTypeValue
Closest Wikipedia entry: Object-oriented programming
Misconceptions about Object32 documented Misconceptions
Check Yourself
AssignmentCopiesObject — Java
Assignment copies the object
ChainedMethodsNotCalledFromOutside — Java
Chained methods are all called on the object at the beginning of the chain
EqualityOperatorComparesObjectsValues — Java
o==p compares the objects referred to by variables o and p
EqualsComparesReferences — Java
o.equals(p) compares the references stored in the variables o and p
FrameIsClassInstance — Java
A stack frame is the same as an instance of a class
MethodAsField — Java
Each object contains its own special fields for all of its methods
MultiReferenceVariable — Java
A reference variable can point to multiple objects
NestedObjectsImplyNestedClasses — Java
If objects are part of a containment hierarchy, their classes are nested, too
NoFieldInheritance — Java
An object contains only the fields declared in its class
NoFieldlessObjects — Java
Objects without instance variables can't exist
NoInsideMethodCallInConstructor — Java
It is foirbidden to call other methods on the same object while inside its constructor
NullIsObject — Java
null is an object
PrimitiveIsObject — Java
Primitive values are heap objects
SuperclassObjectAllocated — Java
When instantiating an object of a subclass, an object of a superclass is also allocated
ThisAsField — Java
this is a special field in the object
ThisAssignable — Java
One can assign to this
ThisExistsInStaticMethod — Java
this is a local variable, also in static methods
VariablesHoldObjects — Java
A variable of a reference type contains a whole object
AccessingInexistentPropertyError — JavaScript
Accessing a non existent property on an object produces an error
AssignmentCopiesObject — JavaScript
Assignment copies the object
EqualityOperatorComparesObjectsValues — JavaScript
The equality operator compares two objects' values
IdentifierAsStringInBracketNotation — JavaScript
An identifier used to access a property with the bracket notation is treated as a string
NoBracketNotationForObjects — JavaScript
Square brackets cannot be used to access properties of an object
NoGlobalObject — JavaScript
There isn't a global object
NullIsObject — JavaScript
null is an object
ObjectAsParameterIsCopied — JavaScript
Objects are passed by value
ThisAssignable — JavaScript
One can assign to this
AssignmentCopiesObject — Python
Assignment copies the object
ObjectsMustBeNamed — Python
A variable is needed to instantiate an object
SelfAssignable — Python
Reassigning self changes the object on which a method is called
VariablesHoldObjects — Python
A variable contains a whole object
EqualityOperatorComparesListIdentities — Scratch
(list a) = (list b) compares the identities of list a and list b